The present invention relates to the field of image restorage of smeared photographic images.
Restoration of smeared photographic images has used optical spatial filtering to reduce smearing effects present in the input image. In such techniques, a spatial filter with a transfer function proportional to the inverse of the Fourier transform of the blur function is employed to restore the original image.
In a recent paper "Deconvolution Using a Joint Transform Correlator"; B. Javidi et al.; Opt. Commun. 70, 369-372, (1989), a binary nonlinear joint transform correlator is described that can perform image deconvolution in real time. In this technique, both the degraded image and the blur function are displayed side by side at the input plane of the joint transform optical correlator. The joint power spectrum (JPS) is obtained using a Fourier transform lens and a square law device such as a CCD array image sensor. The exact Fourier phase of the original image is recovered in the joint power spectrum from the multiplication of the Fourier transform of the smeared image by the conjugate of the Fourier transform of the smearing function.
A hard clipping nonlinearity is used to threshold the joint power spectrum to only two values 1 and -1. The effect of the nonlinearity is to remove the distorted amplitude entirely while retaining the correct phase of the original signal. An amplitude mask averaged over an ensemble of images can be used at the Fourier plane to provide an estimate for the Fourier amplitude component. An inverse Fourier transform of the averaged amplitude and the recovered correct Fourier phase information then yields the original image with reduced distortion.